1. Field of the Invention
The present invention relates generally to wireless headphones and, more particularly, is directed to a wireless headphone and a wireless headphone system in which a satisfactory receiving condition is always maintained regardless of the condition and position of the listener's head.
2. Description of the Prior Art
A wireless headphone system has recently been developed, in which a signal is transmitted through infra-red rays from a transmitter and received at a position remote from the transmitter, so as to enable a music program or the like to be enjoyed by a listener.
Japanese Laid-Open Patent Gazette No. 55-82596 describes a wireless headphone utilizing infra-red rays. According to this Laid-Open Patent, the headphone is a wireless-type headphone, so that the usable range in which the user can utilize the headphone is not limited by a headphone cord unlike other prior-art headphones. Further, the use of infra-red rays prevent the wireless headphone from interfering with other radio waves.
In the wireless headphone described in Japanese Laid-Open Patent Gazette No. 55-82596, an infra-red signal transmitted from a transmitter is received by a light receiving element provided on a top portion of a head band portion of the wireless headphone. A signal outputted from the light receiving element is supplied through an amplifier, a demodulating circuit and a reproducing circuit, which are powered by a power supply source such as a secondary battery or the like incorporated within the headphone, so as to demodulate and reproduce the received signal which is then fed to a headphone unit portion. As a result, the headphone unit portion derives a reproduced audible signal from the signal transmitted from the transmitter.
However, the light receiving element is provided only on the top portion of the head band portion, so that, when the listener wears this wireless headphone on his or her head, hairs may cancel the light receiving element. As a result the light receiving element may not be able to receive the infra-red light signal transmitted from the transmitter. In order to correct this problem, it has been proposed to mount the light receiving element on a hanger portion of the wireless headphone. However, this proposal does not fully remove the risk that the light receiving element will be hidden by hairs when the listener wears the wireless headphone. Further, the light receiving element on this wireless headphone can receive a light signal transmitted from only one direction, for example, a front direction. More specifically, because of the directivity of the light receiving element, it can not receive a transmitted light signal from, for example, a rearward direction unless faced in that direction or a signal which has reached the listener's head after having been reflected on a wall or the like. Accordingly, if the listener turns his or her head towards a direction different from the direction in which the transmitter is transmitting along, the transmitted light signal can not be received by the light receiving element, thereby interrupting the reproduced sound heard by the listener. Thus, the moveable range of the listener is severely limited, which decreases the advantages of the wireless headphone.